-----Original Message----- From: Kirk Wallace [mailto:[email protected]] Sent: Wednesday, March 16, 2011 3:35 PM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] Spindle speed control through G540 VFD output
On Wed, 2011-03-16 at 21:05 +0000, andy pugh wrote: > On 16 March 2011 20:50, Michael Jones <[email protected]> wrote: > > > And yes, the pot is isolated as you've said. > > > > Does this mean that this upgrade is a "not recommended" or possibly > > hazardous direction, or just that there's more I need to do besides just > > hooking up the VFD output pins from the G540 to make it work > > correctly/safely without breaking something? > > It should be fine, but you need to know how "isolated" the VFD output is. > I had a KBIC speed controller and the low side of the pot was held at > +Motor voltage (100V) > The VFD output has it's own GND terminal, which is a good sign. > > http://www.cnczone.com/forums/gecko_drives/88165-g540_vfd_output_floating.ht ml > Has a comment from Mariss (who is Mr Gecko) saying that it will be OK. > "The analog output is optically isolated from both the G540 and the PC. - Mariss" This quote doesn't instill much confidence, but it seems that the G540 terminals 7 Ground, 8 Output, 9 +10V are isolated from the Gecko circuit and float. I am guessing these terminals are implying a potentiometer like function in the G540. The +10V terminal is were you would connect the +10V output from the KBIC to a potentiometer. Ground connects to the ground from KBIC potentiometer terminal for the far end of the potentiometer from the +10V. Then the output terminal (8) and an EMC2 digital PWM signal go to the potentiometer wiper. Current KBIC --------------- GND Wiper +10 | | | | V | +-----------+ Potentiometer New KBIC --------------- GND Wiper +10 | | | | | | GND OutP +10V 7 8 9 G540 ^ | Parport 14 The wiper will be controlled by the EMC2 PWM on parallel port pin 14 VFD PMW (50Hz). See here for the EMC2 HAL setup: http://linuxcnc.org/docs/html/examples_spindle.html#r1_2 The PWM frequency will be determined by the thread rate that the PWM component is loaded in - usually the servo thread or 1kHz (?). The G540 doc hints at 50Hz, but I think it will work anyway. This is off the top of my head, so check the above for yourself. I suspect you could wire the terminals directly, but there is a possibility that current limit resistors might be needed somewhere. ------------------------------------------- Thanks VERY much for the input everyone. I'm thinking I'm going to try setting it up this weekend. I'm thinking I'll put a switch on the center leg of the potentiometer so that I can switch between EMC controlled and manual mode when needed. And JUST as I'm going to start looking at the configuration, HAL files and the like.. the machine boots into "busybox CLI " mode.. Arrrrgh! .. mutter mutter mutter.. ------------------------------------------------------------------------------ Colocation vs. Managed Hosting A question and answer guide to determining the best fit for your organization - today and in the future. http://p.sf.net/sfu/internap-sfd2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
